This invention relates generally to improvements in methods and apparatus for hair removal and, more particularly, to a new and improved system capable of long term and/or permanent mass or individual hair removal from a biological subject by appropriate iontophoretic delivery of a depilatory agent.
It is common practice among most of the world's population to remove hair in order to improve personal appearance. The female is especially desirous of removing unwanted hair on the face, underarms, legs and other anatomical parts that may be exposed because of current fashions such as bikini bathing suits and the like. Besides genetic factors that lead to excess hair, modern medicine, notably steroids, also contribute to this cosmetic concern. The most popular means of hair removal is accomplished primarily by shaving with either a razor blade or electric shaver. Other means include tweezers, wax and depilatories. While these prior art methods have significant disadvantages such as cuts from razors, pain from tweezers and associated risk of infection, messiness of depilatories together with risk of irritation from such harsh chemicals, the common denominator that threads through this group is that such hair removal is usually only temporary. Therefore, such hair removal procedures must be repeated endlessly.
While depilatories have enjoyed relatively wide success as a temporary hair removal expedient, they have not proven successful where longer term or permanent hair removal is desired.
Currently, the most commonly used chemical depilatories are mercaptans, particularly salts of thioglycolic acid. The thioglycolates were patented in the 1930's for use in dehairing cattle hides. By the 1940's, cosmetically elegant alkaline creams containing thioglycolates were patented for human use, and they remain the standard chemical depilatories used today.
Thioglycolate depilatories work by hydrolyzing disulfide bonds. Hair strength is a function of the disulfide bonds between cystine molecules. Cystine forms 15 percent of the keratin in hair and 2 percent of the keratin in skin. This is why thioglycolates preferentially hydrolyze the keratin in hair over that in skin.
Modern formulations are usually aqueous solutions of thioglycolic acid mixed with alkali such as sodium hydroxide or calcium hydroxide. In addition to breaking disulfide bonds, these aqueous solutions of thioglycolates provide the important function of hydrating the hair shaft. This quickly gives the hair a jelly-like consistency so that it can be easily wiped away.
Thioglycolate depilatories are marketed as pastes, lotions, or creams. A thick layer is applied to the face so that the depilatory does not dry out and lose effectiveness. Depending on the formulation, the depilatory is left on for between two and fourteen minutes. After the preparation is removed, the hairs that remain are typically wiped away with a wash cloth. A moisturizer should also be applied afterward to suppress any irritation.
Depilatories are intended to act deep in the follicle where the hair shaft has not fully keratinized and therefore can rapidly absorb the chemical. As a result, several days usually elapse before the hair shaft is visible above the skin's surface. Also, for reasons that are not completely clear, the hair that regrows usually does not have the stubbly feel of shaven hair.
Although the thioglycolates are safe, adverse effects occur occasionally. Thioglycolate is a known contact allergen, and the fragrances used in depilatory preparations can also cause contact allergy. In addition, the alkalinity of certain preparations can cause an irritant dermatitis if left on the skin too long. Moreover, as previously indicated, hair removal is not permanent and hair regrowth is inevitable.
While thioglycolates are the most commonly used depilatories, they are not suitable for all situations. In particular, they are usually too slow in action to be useful to men with thick beards. Many men, especially blacks, suffer from pseudofolliculitis barbae ("razor bumps") in which the sharp tip of the shaven beard hair curls into the adjacent skin and causes a foreign body inflammatory reaction. Chemical depilation can help alleviate this problem by eliminating the possibility of nicking the "razor bumps" and by preventing stubbly, sharp-tipped hair from growing in. However, thioglycolates do not penetrate thick beard hairs rapidly enough to be a practical alternative to shaving. Instead, preparations based on strontium sulfide or barium sulfide must be used. These are more effective for removing thick beard hair within a reasonable period of time. However, sulfide depilatories are seriously limited by the foul odors released by hydrogen sulfide gas. This odor can be minimized by preventing water from coming in contact with the cream. However, even if nearly all of the cream is scraped off, some foul odor is almost always produced when the face is washed, and this has proven to be a significant deterrent to use of these products.
The only known permanent means for hair removal has been by way of electrolysis needle. This latter process is costly, painful, subject to scarification and extremely tedious since it treats only one hair at a time. Moreover, the electrolysis hair removal process often extends over a period of years.
While attempts have also been made to remove hair by iontophoresis and electroosmosis, such processes have not generally been as successful as desired and have been known to produce deleterious side effects.
Hence, those concerned with the development and use of hair removal systems and procedures have long recognized the need for improvements in hair removal methods and apparatus to enable more rapid, reliable, comfortable, convenient, economical, long term and/or permanent mass and/or individual removal of hair. As will become apparent from the ensuing discussion, the present invention fulfills all of these needs.